1. Field of the Invention
This invention relates to a preformed membrane comprising a bitumen/thermoplastic rubber layer, which membrane is suitable for road surfacing and maintenance. Further, this invention relates to the use of this membrane on a surface, preferably using a tack coat, and to certain novel mixtures of bitumen and thermoplastic rubbers.
2. Description of the Prior Art
Road repair, while always a significant problem, is now quickly becoming a critical problem in the United States. Road surfaces are aging and crumbling while the money available to communities to repair roads is shrinking. One means to lower repair costs and improve wear resistance is through use of preformed membranes. Preformed membranes, which are suitable for road surfacing or road repair and which comprise a bitumen/rubber layer are known, e.g., from U.S. Pat. Nos. 3,853,682 and 3,930,100. However, these membranes are far from ideal.
Membranes formed from a bitumen/thermoplastic rubber layer have to fulfill a number of requirements. They must be sufficiently flexible at low ambient temperatures to prevent the formation of cracks, have sufficient consistency at high ambient temperatures to withstand high traffic loads, have sufficient binding capability to retain chippings, show a good weathering resistance, and a high penetration index. With preformed membranes comprising such a layer it would be possible to extend the period in the year when resurfacing and maintenance can be carried out. It would furthermore be possible to use the road immediately after the membrane has been laid. It has now been found that these targets can be met by using a special mixture of bitumen and thermoplastic rubbers.